Active magnesium halide carriers useful in the preparation of catalyst components for olefin polymerization are well known in the art. A usual active magnesium halide carrier is an adduct of a magnesium halide and an alcohol, generally in the form of spheric particles. Spheric catalyst components are obtained by reacting the magnesium halide-alcohol adduct carrier with a titanium compound, such as a titanium halide, and an electron donor compound. When used in olefin polymerization, in particular in propylene polymerization, such catalyst components exhibit high polymerization activities and high stereospecificities, and the resulting polymers have good particle morphology.
The disclosed magnesium halide-alcohol adduct carriers comprise generally only magnesium dichloride and an alcohol. Some of the disclosed magnesium halide-alcohol adduct carriers further comprise a minor amount of water. Such magnesium halide-alcohol adduct carriers may be prepared by known processes, such as spray drying process, spray cooling process, high-pressure extruding process, or high speed stirring process. See, for example, U.S. Pat. No. 4,421,674, U.S. Pat. No. 4,469,648, WO 08707620, WO 9311166, U.S. Pat. No. 5,100,849, U.S. Pat. No. 6,020,279, U.S. Pat. No. 4,399,054, EP 0395083, EP-A-700936, CN 1034736, CN 1463990, CN 1580136, U.S. Pat. No. 6,127,304 and U.S. Pat. No. 6,323,152.
WO98/44009 discloses an adduct of formula MgCl2.mROH.nH2O, wherein R is a C1-C10 alkyl, 2≦m≦4.2, and 0≦n≦0.7. The X-ray diffraction pattern of the adduct is characterized in that, in the range of 2θ diffraction angles between 5° and 15°, there are three main diffraction lines at diffraction angle 2θ of 8.8±0.2°, 9.4±0.2° and 9.8±0.2°, the intensest diffraction line being the one at 2θ of 8.8±0.2°, the intensity of the other two diffraction lines being at least 0.2 times the intensity of the intensest diffraction line. Besides the above-described X-ray diffraction pattern, the above adduct is further characterized by its differential scanning calorimetry (DSC) profile, in which no peaks are present at temperatures below 90° C. or, even if peaks are present below said temperature, the fusion enthalpy associated with said peaks is less than 30% of the total fusion enthalpy.
WO2003/082930 discloses an adduct of formula MgCl2.mEtOH, wherein 2.5≦m≦3.2. The adduct optionally contains water up to 1 wt % based on the total weight of the adduct. The X-ray diffraction pattern of the adduct is characterized in that, in the range of 2θ diffraction angles between 5° and 15°, there are three main diffraction lines at diffraction angle 2θ of 8.8±0.2°, 9.4±0.2° and 9.8±0.2°, the intensest diffraction line being the one at 2θ of 8.8±0.2°, the intensity of the other two diffraction lines being at least 0.2 times the intensity of the intensest diffraction line. The DSC profile of the adduct is characterized by a highest melting temperature peak over 109° C. and an associated fusion enthalpy of 103 J/g or lower.
WO2004/026920 discloses an adduct of formula MgCl2.mEtOH.nH2O, wherein 3.4≦m≦4.4, and 0≦n≦0.7. The X-ray diffraction pattern of the adduct is characterized in that, in the range of 2θ diffraction angles between 5° and 10°, there are at least two diffraction lines at 2θ of 9.3±0.2° and 9.9±0.2°, the intensest diffraction line being the one at 2θ of 9.3±0.2°, the intensity of the other diffraction line being lower than 0.4 times the intensity of the intensest diffraction line. The DSC profile of the adduct is characterized in that there is only one melting peak in a range of from 90 to 105° C.
Besides the above-mentioned magnesium halide-alcohol binary adduct carriers, the prior art also discloses other forms of active magnesium halide carriers. For example, CN1922212A discloses a carrier obtained by reacting a solution of a magnesium halide in a cyclic ether and an alcohol with a titanium halide. CN101190953A discloses a magnesium-containing adduct carrier formed by reacting a C1-C5 alcohol with powdery magnesium in the presence of a methyl halide. CN1590415A discloses a complex carrier prepared by reacting a C2-C4 lower alcohol with powdery magnesium in the presence of a methyl halide to form a homogeneous magnesium compound solution and supporting the formed magnesium compound on a spheric silica carrier. CN1016422B, CN1177868C, CN101056894A, U.S. Pat. No. 4,727,051, CN1255436C, U.S. Pat. No. 5,034,361, U.S. Pat. No. 5,849,655, U.S. Pat. No. 5,817,591 and U.S. Pat. No. 4,469,648 disclose active magnesium dichloride carriers prepared by using an alkoxy magnesium as a starting material.